代码如下:
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Drawing;
namespace Chen
{
/// <summary>
/// HandlerImageOpener 的摘要说明
/// </summary>
public class HandlerImageOpener : IHttpHandler
{
public HandlerImageOpener()
{
//
// TODO: 在此处添加构造函数逻辑
//
}
private string _path = "";
/// <summary>
/// 水印图片路径
/// </summary>
public string PngPath
{
get
{
if (_path == "")
{
_path = System.Web.HttpContext.Current.Server.MapPath(ConfigurationManager.AppSettings["WatermarkedImagePath"]);
}
return _path;
}
}
/// <summary>
/// 为图片加水印并写入到Response.OutputStream
/// </summary>
/// <param name="hc">上下文对象</param>
public void GetNewBitMap(HttpContext hc)
{
// 加载原图片
//System.Web.HttpContext.Current.Response.Write(System.Drawing.Image.FromFile(hc.Request.PhysicalPath));
//System.Web.HttpContext.Current.Response.End();
Bitmap oldBmp = new Bitmap(System.Drawing.Image.FromFile(hc.Request.PhysicalPath));
int newWidth = oldBmp.Width;
int newHeight = oldBmp.Height;
if (oldBmp != null)
{
// 绑定画板
Graphics grap = Graphics.FromImage(oldBmp);
// 加载水印图片
Bitmap bt = new Bitmap(PngPath);
// 水印位置控制
int pH = GetNewPoint(newHeight, bt.Height, true);
int pW = GetNewPoint(newWidth, bt.Width, false);
if (newHeight < pH * 8)
pH = pH / 2;
if (newWidth < pW)
pW = pW / 2 / 2;
int pX = newHeight - pH;
int pY = newWidth - pW - 3;
// 添加水印
grap.DrawImage(bt, pY, pX, pW, pH);
// 写入到输出流
oldBmp.Save(hc.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
}
}
// 控制宽高
private int GetNewPoint(int oldP, int newP, bool isW)
{
int p = 4;
if (isW)
{
p = 16;
}
if (oldP < (newP * p))
{
newP /= 2;
if (oldP < (newP * p))
{
GetNewPoint(oldP, newP, isW);
}
}
return newP;
}
#region IHttpHandler 成员
bool IHttpHandler.IsReusable
{
get { return true; }
}
void IHttpHandler.ProcessRequest(HttpContext context)
{
GetNewBitMap(context);
}
#endregion
}
}
生成.dll文件后在web.config 中配置
<!--水印图片路径-->
<appSettings>
<add key="WatermarkedImagePath" value="~/logo.gif"/>
</appSettings>
<!--引用处理函数 path为需要加水印图片的目录-->
<httpHandlers>
<add type="Chen.HandlerImageOpener, Chen" verb="*" path="image/*.jpg,image/*.gif,image/*.png,image/*.bmp" />
</httpHandlers>

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